In the production of food, in particular in the production of meat and sausage products, there is a plurality of individual devices in the production line, the function of each of which must be coordinated with one another. Until now, conventional cables and connectors have been used in the transmission of process data for Ethernet-based fieldbus systems. In the case of machines used in harsh environments, cables and connectors often lead to malfunctions, standstills and breakdowns.
In the case of electrical plug-in connectors, the connector pin and the associated socket contact in particular are susceptible to mechanical damage, contamination and corrosion when the plug-in connector is in an unmated state. In the case of most of the plug-in connectors available on the market, even water or cleaning chemicals can penetrate through the plug-in connector into the cable when these connectors are in an unmated state, and permanently damage these through corrosion. The transition from the connector pin or socket contact respectively to the cable is likewise subject to a high risk of oxidation due to the different materials. This leads to high contact resistances and leakage currents.
Data transmission by means of WLAN or Bluetooth is currently used as an alternative to the transmission of process data by means of cables.
FIG. 7 shows a corresponding solution. Existing standards are used for the radio transmission. The frequency band lies within the range of 2.4 or 5 or 60 GHz, for example WLAN 802.11X or Bluetooth 3.0+HS.
As a rule, a WLAN comprises an access point and a plurality of participants, which share the available bandwidth as is particularly evident from FIG. 7. The individual devices A, B, C thereby communicate with the corresponding access point/router. Here, fault detection, collision recognition and arbitration mechanisms are necessary. This makes it difficult to estimate the temporal behavior, and makes the response times unpredictable. Bluetooth offers similar capabilities and has similar disadvantages.
But even this solution has disadvantages in that it is relatively slow as compared to cable connections, and in particular, is susceptible to radio interference. In addition, in particular in the case of a plurality of transmitters, there is the disadvantage that the receiver must be adjusted to the desired transmitter, which involves a considerable configuration effort and creates a source of errors. Few radio frequencies are available. If a plurality of transmitters and receivers are operated within range, malfunctions will occur due to adjacent transmitters. The bandwidth must be shared with other devices. If the available bandwidth is not sufficient, it will not be possible to operate the devices simultaneously. A suitable radio channel must be selected and adjusted. The temporal allocation of the transmission capacity likewise plays a role, so that it is necessary to wait for a free channel and in addition, the repetition of the transmission in the event that there is interference in the reception takes time. Changing channels when new malfunctions arise also takes time. In addition, this method is not deterministic. It is not possible to predict how long a successful transmission will take. All told, no transmission of process data in can be performed in real time.